In proton exchange membrane (PEM) type fuel cells, the hydrogen-based feed gas is supplied to an anode of the fuel cell and an oxidant is supplied to a cathode of the fuel cell. PEM fuel cells include a membrane electrode assembly (MEA) comprising a thin, proton transmissive, non-electrically conductive, solid polymer membrane-electrolyte having the anode on one of its faces and the cathode on the opposite face. The MEA is sandwiched between a pair of electrically conductive elements which serve as current collectors for the anode and cathode and contain appropriate channels and/or openings therein for distribution of the fuel cell's gaseous reactants over the surfaces of the respective anode and cathode catalysts.
Typically, atmospheric air is used as the oxidant in PEM systems. Primarily, air comprises nitrogen and oxygen, among other chemical compounds. When air is used as the oxidant in the PEM, the force of the partial pressure of the nitrogen in the air across the PEM will drive some of the nitrogen in the air to permeate through the PEM into the anode. In addition, over time, passages may develop in the MEA which facilitate an additional flow of nitrogen into the anode. The nitrogen that permeates into the anode dilutes the hydrogen based feed gas, thus reducing the efficiency of the PEM fuel cell.
Generally, in order to improve the efficiency of the PEM due to the diluted hydrogen feed gas, the nitrogen diluted hydrogen feed gas is removed from the anode at regular intervals. Typically, an evacuation valve is used to enable the diluted hydrogen feed gas to exit the anode of the PEM. This process, however, results in the waste of hydrogen feed gas as the amount of nitrogen in the anode is hard to predict. Accordingly, it is desirable to create a system to accurately determine the amount of nitrogen in the hydrogen feed gas to reduce the waste of hydrogen feed gas.